Functions
• Support Surrounding Tissue
• Protect Vital Organs and Soft
Tissue
• Provide an Attachment Place for
Muscle
– Bones act as levers to produce
movement
Functions
• Produce Red Blood Cells
–Bone Marrow
• Storage of Minerals
–Calcium & Phosphorus
• Fat Storage
Haversian
Canal
Lacuna with
Osteocyte
Canaliculi
Microscopic Anatomy of Compact Bone
Matrix
– 25% water, 25% collagen fibers, 50%
mineral salts
Cells
• Osteogenic cells in periosteum 
• Osteoblasts
– Secrete collagen fibers and build matrix
– With time, they become 
Microscopic Anatomy of Compact Bone
Cells (continued)
• Osteocytes that maintain bone
• Osteoclasts digest bone matrix for normal
bone turnover
Microscopic Anatomy of
Compact Bone
• Arranged in osteons (Haversian systems)
– Cylinders running parallel to long axis of
bone
• Haversian Canal: a.k.a. central canal;
contain blood vessels, neurons
• Lacuna: means “little lake”; they
house bone cells
Microscopic Anatomy of
Compact Bone
• Canaliculi: “small canal”; Permit
flow of ECF between central canal
and lacunae
• Perforating (Volkmann’s) canals
– Carry blood and lymphatic vessels and nerves
from periosteum
– They supply central (Haversian) canals and
also bone marrow
Spongy Bone
• Not arranged in osteons
• Irregular latticework of trabeculae
– These contain lacunae with osteocytes and
canaliculi
• Spaces between trabeculae may contain
red bone marrow
• Spongy bone is lighter than compact bone,
so reduces weight of skeleton
Classification of Bones
1. Long Bones
a. Examples: femur, radius, ulna
b. Diaphysis: Shaft; composed of
compact bone
c. Epiphysis: End of long bone;
composed of spongy bone;
Classification of Bones
2. Short Bones
a. Cube-shaped; spongy bone
surrounded by a thin layer of
compact bone
b. Includes carpals and tarsals
Classification of Bones
3. Flat Bones
a. Spongy bone within two plate-like
coverings of compact bone
b. Protect; provide surface area for
muscles;
ribs, sternum, skull bones
4. Irregular Bones
a. Include vertebrae, scapula
Classification of Bones
5. Sesamoid Bones
•
•
small, flat, and shaped somewhat like a
sesame seed
Develop inside tendons and are most
commonly found near joints at the knees,
the hands, and the feet
• Example: patella
Classification of Bones
6. Sutural (Wormian) Bones
• small, flat, irregularly shaped bones
between the flat bones of the skull
• individual variations in the number, shape,
and position
• range in size from a grain of sand to the
size of a quarter
Anatomy of A Long Bone
1. Diaphysis
a. Made of compact bone; covered by a
tough membrane, the periosteum
b. Central Cavity called the Medullary
cavity
1) In children: filled with red marrow
2) Adults: marrow replaced by fat
3) Inner lining = endosteum
Anatomy of A Long Bone
2. Epiphysis (Plural: epiphyses)
a. The end(s) of long bone
b. Made of a thin layer of compact
bone on the outside
c. Spongy bone on the inside
Anatomy of A Long Bone
d. Enlarged for muscle attachment,
joint formation
e. Site of hemopoiesis in adults (red
marrow)
f. Articular cartilage covers surface
(hyaline)
Anatomy of A Long Bone
3. Epiphyseal Disk (Line)
a. Flat plate of hyaline cartilage
b. Site of longitudinal bone growth
(length-wise)
c. At the end of growth, cartilage is
replaced by bone; process is
called fusion
Anatomy of A Long Bone
d. Doctors can predict growth
from x-rays
4. Periosteum: Membrane covering
the diaphysis
a. Essential in bone growth, repair,
and nutrition
b. Contains C.T., osteogenic cells and
osteoblasts
Epiphyseal lines
Articular cartilage
Typical
Long Bone Structure
Spongy bone
Epiphysis (proximal)
Spongy bone (red marrow)
Compact bone
Medullary cavity
Yellow marrow
Periosteum
Diaphysis
Epiphysis (distal)
Structure of Long Bone
Figure 6.3a
Bone Dynamics and Tissue
Interactions Animation
Bone Dynamics and Tissue
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Copyright 2010, John Wiley &
Sons, Inc.
Bone Formation
• Known as ossification
• Timeline
– Initial bone development in embryo and fetus
– Growth of bone into adulthood
– Remodeling: replacement of old bone
– Repair if fractures occur
• Mesenchyme (early connective tissue) model
– This initial “skeleton” model will be replaced by
bone tissue beginning at 6 weeks of embryonic life
Bone Formation
• Two different methods of ossification each
result in similar bone tissue
– Intramembranous: bone forms within sheets of
mesenchyme that resemble membranes
• Only a few bones form by this process: flat bones of the
skull, lower jawbone (mandible), and part of clavicle
(collarbone)
– Endochondrial: mesenchyme forms hyaline
cartilage which then develops into bone
• All other bones form by this process
Intramembranous Ossification
Four steps
1.Development of ossification center
 Mesenchyme cells  osteogenic osteoblasts
 Osteoblasts secrete organic matrix
2.Calcification: cells become osteocytes
 In lacunae they extend cytoplasmic processes to each other
 Deposit calcium & other mineral salts
3. Formation of trabeculae (spongy bone)
 Blood vessels grow in and red marrow is formed
4.Periosteum covering the bone forms from
mesenchyme
Endochondrial Ossification
• Six Steps
1. Formation of cartilage model of the “bone”
• As mesenchyme cells develop into chondroblasts
2. Growth of cartilage model
• Cartilage “bone” grows as chondroblasts secrete
cartilage matrix
• Chondrocytes increase in size, matrix around them
calcifies
• Chondrocytes die as they are cut off from nutrients,
leaving small spaces (lacunae)
Endochondrial Ossification
3. Primary ossification center
– Perichondrium sends nutrient artery inwards into
disintegrating cartilage
– Osteogenic cells in perichondrium become
osteoblasts that deposit bony matrix over
remnants of calcified cartilage  spongy bone
forms in center of the model
– As perichondrium starts to form bone, the
membrane is called periosteum
Endochondrial Ossification
4. Medullary (marrow) cavity
– Spongy bone in center of the model grows toward
ends of model
– Octeoclasts break down some of new spongy
bone forming a cavity (marrow) through most of
diaphysis
– Most of the wall of the diaphysis is replaced by a
collar of compact bone
Endochondrial Ossification
5. Secondary ossification center
– Similar to step 3 except that nutrient arteries enter
ends (epiphyses) of bones and osteoblasts
deposit bony matrix  spongy bone forms in
epiphyses from center outwards
– Occurs about time of birth
6. Articular cartilage and epiphyseal cartilage
– Hyaline cartilage at ends of epiphyses becomes
articular cartilage
– Epiphyseal (growth) plate of cartilage remains
between epiphysis and diaphysis until bone
growth ceases
Perichondrium
Proximal
epiphysis
Uncalcified
matrix
Hyaline
cartilage
Periosteum
Uncalcified
matrix
Diaphysis
Calcified
matrix
Primary
ossification
center
Nutrient
artery
Spongy
bone
Distal
epiphysis
Calcified
matrix
Periosteum
(covering
compact bone)
Medullary
cavity
Nutrient
artery and vein
1 Development of
cartilage model
2 Growth of
cartilage model
3 Development of
primary ossification
center
4 Development of
the medullary
cavity
Articular cartilage
Secondary
ossification
center
Epiphyseal
artery and
vein
Spongy bone
Uncalcified
matrix
Epiphyseal plate
Nutrient
artery and vein
5 Development of secondary
ossification center
6 Formation of articular cartilage
and epiphyseal plate
Growth In Length
• Chondrocytes divide and grow more cartilage
on epiphyseal side of the epiphyseal plate
• Chondrocytes on the diaphyseal side die and
are replaced by bone
• Therefore bone grows from diaphyseal side
towards epiphyseal side
• Growth in length stops between 18-25 years;
cartilage in epiphyseal plate is completely
replaced by bone (epiphyseal line)
Growth In Width
• As bones grow in length, they must also grow
in thickness (width)
– Perichondrial osteoblasts  osteoblasts  lay
down additional lamellae of compact bone
– Simultaneously, osteoclasts in the endosteum
destroy interior bone to increase width of the
marrow
Bone Surface Markings
1. Depressions & Openings
A. Foramen: hole through which blood
vessels and nerves pass (ex. Foramen
magnum)
B. Meatus: passage extending within a
bone (ex. External auditory meatus)
C. Fossa: ditch or shallow depression on
a bone (ex. Mandibular fossa of
temporal bone)
2. Processes that form joints
A. Condyle: large rounded
prominence forming a joint
B. Head: rounded projection that
forms a joint (ex. Head of femur)
C. Facet: smooth, flat surface (ex.
Facet of vertebrae)
3. Processes to which tendons &
ligaments attach
A. Tuberosity: large rounded projection
with a rough surface (ex. Deltoid
tuberosity of humerus)
B. Spinous process: sharp, slender
projection (on vertebrae)
C. Crest: Prominent ridge (ex. illiac crest
of pelvic bone)
D. Trochanter: large, blunt projection
(only on femur)
Bone Quizzes
1. Functions, microscopic anatomy,
classification
2. Long bone anatomy, bone “markings”
3. Bone homeostasis, articulations
Bone Remodeling & Maintenance
Constantly changing due to the needs of
the body
Chemical changes/homeostasis
• If blood Ca+2 levels are too low, PTH is
released;
• causes bone absorption (destruction);
this elevates Ca+2 levels
Bone Remodeling & Maintenance
• PTH, parathyroid hormone is
produced by the parathyroid gland
• If blood calcium levels are too high,
calcitonin is released; causes Ca+2 to
be deposited onto bone;
• Ca+2 levels in the blood then drop
Bone Remodeling & Maintenance
• Calcitonin is a hormone produced by
the thyroid gland
Mechanical Stresses
• Gravity
• Muscle Tension (from exercise)
Homeostasis of Bone Tissue
Vitamin D
1. Stimulates absorption of calcium in
small intestine
2. Promotes reabsorption of Calcium by
the kidneys
3. Inihibits PTH production
Importance of Ionic Calcium
in the Body
• Calcium is necessary for:
–Transmission of nerve impulses
–Muscle contraction
–Blood clotting
–Secretion by glands and nerve cells
–Cell division
Articulations
Articulations & Joints; Functions:
• Hold bones together (includes
ligaments)
• The structure of a joint determines the
type of movement that may occur
• Each joint reflects some compromise
between strength and mobility.
Articulations
Types of Joints
• Synarthroses: “without joint”; joints
that allow no movement
– Bones connected by fibrous or cartilage
tissue; STRENGTH, no mobility
– There are 4 types; we need to know only
one
– Example: skull sutures
Articulations
Amphiarthroses: allow slight movement;
compromise between mobility and strength
• Bones are connected by collagen fibers or
cartilage
• At a syndesmosis (desmos, a band or ligament),
bones are connected by a ligament; tibia/fibula
• At a symphysis, the bones are separated by a pad
of fibrocartilage; pubic symphysis
Articulations
Diarthroses: freely moveable joints;
also called synovial joints
• surrounded by a fibrous articular
capsule, and a synovial membrane
lines the cavity
• Synovial joints may have a variety of
accessory structures, including pads of
cartilage or fat, ligaments, tendons, and
bursas
Articulations
Diarthroses (continued)
• Nonaxial joints: allow only
sliding movement to occur
between bones:
• Sometimes called gliding joints
–ankle, wrist
Articulations
Diarthroses (continued)
• Uniaxial joints: allow mvt in one
plane
–hinge type: elbow
– pivot type: radius/ulna
• Biaxial joints: allow mvt in two
planes
–knuckles
Articulations
Diarthroses (continued)
• Multiaxial: allow movement in all
planes
–ball & socket: shoulder and hip
Articulations
All diarthrotic joints have 4
distinguishing characteristics:
(1) articular cartilage
(2) fibrous articular (joint) capsule
(3) joint cavity
(4) reinforcing ligaments
• Skull
–Cranial bones (8) and facial bones
(14)
• Vertebral Column
–5 regions
–4 curves
• Bony Thorax
–Ribs and sternum
• Air-filled, mucous-membrane lined
cavities within certain bones
• 4 pairs found in the ethmoid, frontal,
maxillae, and sphenoid bones
• Lighten the bone
• Warm the air
• Provide resonance in speech
Upper Limb:
• Pectoral (shoulder) Girdle
–Scapula and clavicle
• Bones of the arms and hands
Lower Limbs:
• Pelvic (hip) Girdle
–Os coxae (ileum, ischium,
pubis)
• Bones of legs and feet
Comparison of Male and
Female Pelves
Table 7.4.2